PubMed · 13381939
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A CESANELLI, A SERIAL. [Torulopsis lung].. https://pubmed.ncbi.nlm.nih.gov/13381939/
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The epidemiology data for candidiasis indicate an increase in Candida glabrata infections. Moreover, several reports have shown an increasing number of drug-resistant cases of these infections. The source of drug resistance can often be traced to genetic mutations in genes related to a drug's mechanism of action. Therefore, we conducted whole genome sequencing of several drug-resistant isolates of Candida glabrata collected from patients hospitalized in Eastern Poland to assess whether mutations in selected genes correlated with susceptibility analysis results. The fungal species from patient samples were identified, and the isolated Candida glabrata were subjected to antifungal drug susceptibility testing. The results were interpreted according to the EUCAST and CLSI recommendations. Susceptibility to 5-flucytosine was assessed using the ATB FUNGUS kit. Libraries were prepared according to the NEXTERA XT DNA Library Prep and subsequently sequenced. The outcomes indicated common resistance to two of the three analyzed echinocandins, as well as two cases of simultaneous resistance to echinocandins and selected azole-based drugs. We detected several previously reported mutations in selected resistance-related genes, as well as five that are first described here: ERG5 (M267I), ERG6 (R57K), PDH1 (K438Q, V434I, F600V, V1192S), FCY1 (M129T), and FCY2 (I384F). Neither of the identified nonsynonymous mutations was correlated with the drug resistance demonstrated in the susceptibility testing. Furthermore, we can exclude the possibility of acquired drug resistance, thereby raising questions about the possibility of unknown mechanisms of resistance to azole-based and echinocandin drugs.
Pyruvate production by Torulopsis glabrata was used as a model to study the mechanism of product inhibition and the strategy for enhancing pyruvate production. It was found that the concentration of cell growth and pyruvate deceased with the increase of NaCl and sorbitol concentrations. To enhance the osmotic stress resistance of the strain, an NaCl-tolerant mutant RS23 was screened and selected through a pH-controlled continuous culture with 70 g/L NaCl as the selective criterion. Compared with the parent strain, mutant RS23 could grow well on the medium containing 70 g/L NaCl or 0.6 mol/L sorbitol. Pyruvate concentration by the mutant strain RS23 reached 94.3 g/L at 82 h (yield on glucose 0.635 g/g) in a 7-l fermentor with 150 g/L glucose as carbon source. Pyruvate concentration and yield of mutant RS23 were 41.1% and 11.1% higher than those of the parent strain, respectively. The strategy for enhancing pyruvate production by increasing osmotic stress resistance may provide an alternative approach to enhance organic acids production with yeast.
We investigated patterns of rate asymmetry in sequence evolution among the gene pairs (ohnologs) formed by whole-genome duplication (WGD) in yeast species. By comparing three species (Saccharomyces cerevisiae, Candida glabrata, and S. castellii) that underwent WGD to a nonduplicated outgroup (Kluyveromyces lactis), and by using a synteny framework to establish orthology and paralogy relationships at each duplicated locus, we show that 56% of ohnolog pairs show significantly asymmetric protein sequence evolution. For ohnolog pairs that remain duplicated in two species there is a strong tendency for the faster-evolving copy in one species to be orthologous to the faster copy in the other species, which indicates that the evolutionary rate differences were established before speciation and hence soon after the WGD. We also present evidence that in cases where one ohnolog has been lost from the genome of a post-WGD species, the lost copy was likely to have been the faster-evolving member of the pair prior to its loss. These results suggest that a significant fraction of the retained ohnologs in yeast species underwent neofunctionalization soon after duplication.